CD3-positive plasmablastic B-cell neoplasms: a diagnostic pitfall

Celastrol ameliorates lupus by promoting apoptosis of autoimmune T cells and preventing autoimmune response in MRL/lpr mice

OBJECTIVE

Celastrol is a bioactive constituent extracted from Tripterygium wilfordii (thunder god vine). It has been demonstrated to have a therapeutic effect on experimental disease models for chronic inflammatory and immune disorders. In the present study, we investigated whether and how celastrol exerts a regulatory effect on the autoimmune response in MRL/lpr mice.

METHODS

We performed an in vivo study to determine the therapeutic effects of celastrol in MRL/lpr mice and then further investigated the underlying mechanism of celastrol in the regulation of the autoimmune response in MRL/lpr mice.

RESULTS

Celastrol showed a therapeutic effect in MRL/lpr mice by preventing the enlargement of the spleen and lymph nodes, alleviating renal injury, and reducing the levels of ANA and anti-double-stranded DNA antibodies. Furthermore, celastrol suppressed the in vivo inflammatory response in MRL/lpr mice by reducing the serum levels of multiple cytokines, including interleukin (IL)-6, tumour necrosis factor (TNF) and interferon (IFN)-γ, and the production of multiple antibody subsets, including total IgG, IgG1 and IgG2b. In vitro, celastrol reduced anti-CD3 antibody stimulation-induced T helper 1 and TNF-producing cells in CD4+ T cells of MRL/lpr mice. In addition, celastrol significantly affected B cell differentiation and prevented the generation of plasma cells from B cells in MRL/lpr mice by reducing the frequency of activated and germinal centre B cells. Celastrol treatment also affected T cell differentiation and significantly reduced central memory T cell frequencies in MRL/lpr mice. Importantly, celastrol treatment specifically promoted apoptosis of CD138+ but not CD138- T cells to suppress autoimmune T cell accumulation in MRL/lpr mice.

CONCLUSIONS

Celastrol exerted therapeutic effects on lupus by specifically promoting apoptosis of autoimmune T cells and preventing the progression of autoimmune response.

CD138 promotes the accumulation and activation of autoreactive T cells in autoimmune MRL/lpr mice

Autoreactive T cells, specifically CD138+ (syndecan-1) T cells produced in Fas-deficient systemic lupus erythematosus (SLE) mouse models, were shown to significantly promote the generation of autoantibodies. In the present study, Murphy Roths Large lymphoproliferative (MRL/lpr) lupus mice were used to investigate the role of CD138 protein expression in T cells in the progression of SLE. Measurement of flow cytometry, immunofluorescence and Luminex were performed to determine the effect of CD138 on T cells in MRL/lpr mice. The results demonstrate that CD138+ T cells induce apoptosis via a Fas-dependent pathway. CD138 protein expression in T cells of MRL/lpr mice significantly reduced T cell apoptosis and contributed to the accumulation of T cells and double negative (DN) T cells, whilst simultaneously promoting T cell activation in Fas-deficient lupus mice. CD138 protein expression in DN T cells also significantly increased the protein expression of Fas ligand to enhance the cytotoxicity of DN T cells. Furthermore, phorbol 12-myristate 13-acetate and ionomycin (PI) stimulation reduced CD138 protein expression in CD3+ T cells and prevented CD138+ T cell accumulation by inducing specific apoptosis. PI stimulation also activated T cells in MRL/lpr mice to increase CD69 protein expression. CD69 protein expression in CD138+ T cells significantly increased the frequency of apoptotic CD138+ T cells. In addition, results from the present study demonstrated that CD138- T cells of MRL/lpr lupus mice had an activation defect. CD138 protein expression in T cells significantly reversed the defective activation and activating T cells could significantly reduce CD138 protein expression in CD3+ T cells of MRL/lpr mice. This suggests that CD138 protein expression in CD3+CD138- T cells of MRL/lpr mice may be a consequence of the impaired activation in autoreactive T cells prior to exposure to self-antigens by the immune system. CD138 expression in autoreactive T cells has a central role in promoting the progression and development of autoimmune response in MRL/lpr mice.

Cervical radiculopathy as first presentation of CD3-positive diffuse large B-cell lymphoma of the cervico-thoracic junction

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) in rare cases can presents an unusual expression of CD3 T-cell specific antigen. We report the first case of a CD3-positive DLBCL of the cervico-thoracic junction presenting with persistent cervical radiculopathy.

CASE PRESENTATION

A 74-years-old male patient presented a severe and persistent right C8 radiculopathy associated with right-sided neck pain, progressive numbness and weakness of the right arm. The symptoms prominent during the night interfering with sleep and were resistant to anti-inflammatory drugs and cervical orthosis. Spine MRI showed a solid hypointense lesion on T2-weighted images and hyperintense on STIR sequences involving the epidural space at C7, T1 and T2. The patient underwent a C7-T1 decompressive laminectomy and left T2 hemilaminectomy with resection of the epidural tissue resulting in subtotal removal. Histology showed a DLBCL germinal center B-cell lymphoma with expression of CD3 T-cell specific antigen. Then the patient underwent adjuvant radiotherapy and chemotherapy consisting of R-CHOP protocol. At last follow-up (2 years) the patient is still in good clinical status (KPS = 80) with almost complete recovery of the cervical radiculopathy.

CONCLUSIONS

To our knowledge this is the first case of DLBLC GCB-like CD3 positive to present with radiculopathy.

A series of heterogeneous lymphoproliferative diseases with CD3 and MUM1 co-expressed in cats and dogs

Lymphoma diagnosis in dogs and cats is continually evolving as new subtypes and human correlates are being recognized. In humans, T-cell lymphomas with MUM1 expressed and plasma cell neoplasia or B-cell lymphomas with CD3 expressed aberrantly are reported only rarely. We report here a case series of tumors in dogs and cats with CD3 and MUM1 co-expressed as determined by immunocytochemistry or immunohistochemistry. Lineage was assigned for these tumors by 3 board-certified pathologists and a veterinary immunologist based on review of clinical and cellular features and the results of ancillary testing including PCR for antigen receptor rearrangements, flow cytometry, and serum protein electrophoresis with immunofixation. In cats, 7 of 7 tumors, and in dogs, 3 of 6 tumors with CD3 and MUM1 co-expressed had clonal rearrangement of the immunoglobulin gene or serum monoclonal immunoglobulin, consistent with a diagnosis of a plasma cell neoplasia or myeloma-related disorder with CD3 expressed aberrantly. Disease was often disseminated; notably, 3 of 7 feline cases had cutaneous and/or subcutaneous involvement in the tarsal area. In dogs, 3 of 6 cases had a clonal T-cell receptor gamma result and no clonal immunoglobulin gene rearrangement and were diagnosed as a T-cell tumor with MUM1 expressed. The use of multiple testing modalities in our series of tumors with plasma-cell and T-cell antigens in dogs and cats aided in the comprehensive identification of the lymphoproliferative disease subtype.

Flow Cytometric Findings in Primary Effusion Lymphoma: A Report of Two Cases

Primary effusion lymphoma (PEL) is a rare B-cell lymphoma that usually occurs in the setting of HIV infection, and it is associated with Human Herpesvirus-8 (HHV-8). Diagnosis of PEL is usually established in cell centrifuge, cell block, or tissue examination, and there are few reports describing flow cytometry findings in PEL. We report two male patients (a 34-year-old and a 56-year-old) with a history of HIV infection. The first patient presented with ascites and abdominal pain, and the second patient presented with chest pain and parapneumonic pleural effusion. Cavitary fluid examination showed large pleomorphic neoplastic lymphoid cells with plasmablastic morphology. Flow cytometry analysis of the neoplastic lymphocytes showed increased forward scatter and side scatter with intermediate to a high level of CD38 expression. In one patient, lymphoma cells showed bright CD45 expression with dim expression of CD19 and kappa light chain. There was no significant expression of CD20 or any T/NK cell markers in either case. Immunohistochemistry for CD30 was positive in one patient. Immunohistochemistry for HHV-8 and in situ hybridization for Epstein-Barr virus-encoded small RNAs (EBER) was positive on cell blocks in both cases, consistent with the diagnosis of primary effusion lymphoma. PEL should be considered in the differential diagnosis of CD20-negative hematopoietic neoplasms, and flow cytometry may provide helpful clues for the diagnosis of PEL as part of the workup for pleural effusion with cytologically malignant cells.

Glucocorticoid prevents CD138 expression in T cells of autoimmune MRL/lpr mice

CD138⁺ T cells, the majority of which are CD4 and CD8 double-negative (DN) T cells, contribute to the production of anti-dsDNA antibodies in a CD4 receptor-dependent way to promote the development of systemic lupus erythematosus (SLE). Accumulation of CD138⁺ T cells in the spleen of MRL/lpr mice was significantly reduced by prednisone. Reduced expression of CD138 in DN T cells induced by prednisone treatment alleviated the accumulation of DN T cells in MRL/lpr mice. The frequency of CD138⁺ cells in CD4⁺ T cells of prednisone-treated MRL/lpr mice was also significantly reduced, which subsequently contributed to reduced production of anti-dsDNA antibody in the prednisone-treated MRL/lpr mice. Additionally, prednisone significantly reduced serum IgG and IgG subsets and simultaneously increased IgM secretion in serum. This suggested that glucocorticoids played a protective role during SLE treatment in MRL/lpr mice by promoting the production of IgM. The present study provides new insights into the mechanism of glucocorticoid for the treatment of SLE.

A Comprehensive Clinicopathologic and Molecular Study of 19 Primary Effusion Lymphomas in HIV-infected Patients

Primary effusion lymphoma (PEL) is associated with human herpesvirus 8 and frequently with Epstein-Barr virus (EBV). We report here a single-center series of 19 human immunodeficiency virus-associated PELs, including 14 EBV+ and 5 EBV- PELs. The objectives were to describe the clinicopathologic features of PELs, with a focus on programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) expression, to search for genetic alterations by targeted deep sequencing analysis, and to compare the features between EBV+ and EBV- cases. All the patients were male, and the median age at diagnosis was 47 years old (interquartile range: 40 to 56 y). Reflecting the terminal B-cell differentiation, immunophenotypic profiles showed low expression levels of B-cell markers, including CD19 (0/19), CD20 (1/19), CD79a (0/19), PAX5 (1/19), BOB1 (3/19), and OCT2 (4/19), contrasting with a common expression of CD38 (10/19), CD138 (7/19), and IRF4/MUM1 (18/19). We observed a frequent aberrant expression of T-cell markers, especially CD3 (10/19), and less frequently CD2 (2/19), CD4 (3/19), CD5 (1/19), and CD8 (0/19). Only 2 cases were PD-L1 positive on tumor cells and none PD-1 positive. With respect to immune cells, 3 samples tested positive for PD-L1 and 5 for PD-1. Our 36-gene lymphopanel revealed 7 distinct variants in 5/10 PELs, with either a single or 2 mutations per sample: B2M (n=2), CD58 (n=1), EP300 (n=1), TNFAIP3 (n=1), ARID1A (n=1), and TP53 (n=1). Finally, we did not observe any major clinical, pathologic, or immunohistochemical differences between EBV+ and EBV- PELs and the outcome was similar (2-y overall survival probability of 61.9% [95% confidence interval, 31.2-82.1] vs. 60.0% [95% confidence interval, 12.6-88.2], respectively, P=0.62).

The many faces of plasma cell neoplasms: morphological and immunophenotypical variants of the great imitator

Plasma cell neoplasms are notorious for having diverse morphological presentations, and less frequently, unusual immunophenotypical profiles. This unexpected immunomorphological variability could lead to erroneous impressions upon initial assessment, potentially delaying the generation of a final accurate diagnosis. In this review, we present a concise, yet comprehensive summary of both morphological and immunophenotypical variants of plasma cell neoplasms from the archives of MD Anderson Hematopathology Department, with emphasis on possible diagnostic pitfalls precluding a timely and accurate assessment.

Resistance of B-Cell Lymphomas to CAR T-Cell Therapy Is Associated With Genomic Tumor Changes Which Can Result in Transdifferentiation

Despite the impressive efficacy of chimeric antigen receptor (CAR) T-cell therapy (CART) in B-cell non-Hodgkin lymphomas, durable responses are uncommon. The histopathologic and molecular features associated with treatment failure are still largely unknown. Therefore, we have analyzed 19 sequential tumor samples from 9 patients, prior anti-CD19 CART (pre-CART) and at relapse (post-CART), using immunohistochemistry, fluorescence in situ hybridization, array comparative genomic hybridization, next-generation DNA and RNA sequencing, and genome-scale DNA methylation. The initial diagnosis was diffuse large B-cell lymphoma (n=6), double-hit high-grade B-cell lymphoma (n=1), and Burkitt lymphoma (n=2). Histopathologic features were mostly retained at relapse in 7/9 patients, except the frequent loss of 1 or several B-cell markers. The remaining 2 cases (1 diffuse large B-cell lymphoma and 1 Burkitt lymphoma) displayed a dramatic phenotypic shift in post-CART tumors, with the drastic downfall of B-cell markers and emergence of T-cell or histiocytic markers, despite the persistence of identical clonal immunoglobulin gene rearrangements. The post-CART tumor with aberrant T-cell phenotype showed reduced mRNA expression of most B-cell genes with increased methylation of their promoter. Fluorescence in situ hybridization and comparative genomic hybridization showed global stability of chromosomal alterations in all paired samples, including 17p/TP53 deletions. New pathogenic variants acquired in post-CART samples included mutations triggering the PI3K pathway (PIK3R1, PIK3R2, PIK3C2G) or associated with tumor aggressiveness (KRAS, INPP4B, SF3B1, SYNE1, TBL1XR1). These results indicate that CART-resistant B-cell non-Hodgkin lymphomas display genetic remodeling, which may result in profound dysregulation of B-cell differentiation. Acquired mutations in the PI3K and KRAS pathways suggest that some targeted therapies could be useful to overcome CART resistance.

Heterogeneity in the diagnosis of plasmablastic lymphoma, plasmablastic myeloma, and plasmablastic neoplasm: a scoping review

The diagnosis of plasmablastic lymphoma (PBL), plasmablastic myeloma (PBM), and plasmablastic neoplasm (PBN) may be arbitrary in some cases because these entities can be indistinct. We conducted this scoping review to investigate heterogeneity in diagnostic criteria used in previous studies and validate the diagnostic results of previous diagnostic algorithms and the algorithm we developed, which also includes diagnosis of PBN. Using the PRISMA Extension for Scoping Reviews, we analyzed literature published between September 2017 and April 2020. We identified a total of 163 cases (128 PBL, 32 PBM, and 3 PBN) from 77 case reports and 8 case series. We found that diagnostic criteria in the literature varied for PBL but were consistent for PBM. Our algorithm was the first attempt to include PBN in a complete structure. The results of the three diagnostic algorithms varied significantly. Hematologists and pathologists should pay more attention to the differential diagnosis of PBL, PBM, and PBN.

CD3-positive plasmablastic lymphoma reported in two cases: A potential diagnostic caveat

Plasmablastic lymphoma (PBL) is a rare aggressive subtype of mature large B cell lymphoma involving almost exclusively the extranodal regions particularly the oral cavity, frequently described in immunocompromised patients. PBL is characterized histologically by diffuse proliferation of large neoplastic cells resembling B immunoblasts or plasmablasts. The diagnosis of PBL can be difficult due to its ambiguous histopathological features mimicking most large cell lymphomas and lacking a distinctive immunophenotypic pattern. They typically lack expression of CD20 and CD79a but may express plasma cell marker, CD138. Aberrant immunoexpression of CD3, a T-cell marker in PBL in the absence of other B-cell markers is exceptionally rare, may potentially lead to incorrect interpretation. Herein, we report a case series of CD3-positive PBL of oral cavity in two individuals, which were initially misdiagnosed as high-grade T-cell lymphomas including extranodal NK/T-cell lymphoma, nasal type. Useful distinguishing clinical settings, histomorphological features, immunohistochemistry and molecular expression profiles of PBL are discussed.

Gastrointestinal Tract Plasmablastic Lymphoma in HIV-Infected Adults: A Histopathological Review

BACKGROUND.

Plasmablastic lymphoma (PBL) is an aggressive B-cell lymphoma that is characterized by the expression of plasma cell antigens and loss of pan B-cell antigens. The neoplasm is extensively reported in the oral cavity and anorectal region but rarely in the gastrointestinal tract, where only isolated case reports and small case series have been reported. In the current study, morphologic, immunohistochemical, and molecular features of 17 cases of gastrointestinal tract PBL were reviewed.

METHODS.

Ten-year retrospective study that reappraised the histomorphological and immunophenotypical profiles of HIV-associated PBLs in the gastrointestinal tract.

RESULTS.

The mean age of the study patients was 41 years with a 3:1 ratio of males to females. The most common site of tumor origin was the small intestine (42%), followed by the stomach (29%) and the colon (29%). Majority of the cases showed a predominant diffuse (82%) growth pattern. Immunoblasts and plasmablasts were observed in all cases. Plasmacytic differentiation was seen in 5 (29%) cases. Additional observations not previously described or emphasized in literature includes pseudo-alveolar growth pattern, centroblast-predominance, multinucleated giant cells, and clear cell change. Immunohistochemistry revealed absence of pan B-cell antigens and expression of plasma cell antigens in all cases. Epstein-Barr virus-encoded RNA was expressed in 53% of the cases.

CONCLUSIONS.

This study highlights the spectrum of histopathological features seen in gastrointestinal tract PBLs. Awareness of this entity and its histopathological features in the gastrointestinal tract is essential for making a timely and accurate diagnosis and improving patient outcomes.

Clinical, pathological and molecular features of plasmablastic lymphoma arising in the gastrointestinal tract: A review and reappraisal

Plasmablastic lymphoma (PBL) is a CD20-negative large B-cell lymphoma with a plasmacytic phenotype and a dismal prognosis, which has been defined as a distinct entity only in the 2008 WHO Classification of Haematopoietic and Lymphoid Tissue and confirmed in the 2017 Edition. Current knowledge of the biological, clinical and prognostic features of PBL is mostly limited, resulting in diagnostic issues, as well as in lack of standard of care and effective therapeutic options. PBL commonly affects the oral cavity of HIV-positive individuals, however the gastrointestinal (GI) tract is the most common extraoral site, and in this location most patients are HIV-negative. In this review, we focus on the clinical, morphological and prognostic features of PBL arising in the GI tract, in order to improve knowledge on this rare, but aggressive disease.

Histologic transformation of t(11;18)-positive MALT lymphoma presented with aberrant T-cell marker expression

Mucosa-associated lymphoid tissue (MALT) lymphoma with t(11;18)(q21;q21), resulting in an API2-MALT1 fusion transcript, is reported to rarely transform into aggressive lymphoma. Here, we report the clinical course of a patient who experienced histologic transformation after 20 years' disease history of t(11;18)-positive MALT lymphoma. The patient suddenly developed a large intrapelvic mass and ascites with a rapid increase in lactate dehydrogenase. Cytology of the ascites detected large abnormal cells, and flow cytometric analysis revealed that the cells were positive for cytoplasmic CD3, CD4, and CD38, and partially positive for CD7, but negative for CD19 and CD20. Antigen receptor gene rearrangement analysis and in situ hybridization of the immunoglobulin light chains confirmed that the tumor cells were of B-cell lineage. Chromosomal analysis showed complex karyotypes with intraclonal variation, and in addition to t(11;18), t(8;14) and heterozygous loss of the TP53 were demonstrated. Although histological and phenotypic features were significantly altered from the original MALT lymphoma, the presence of t(11;18) led us to the diagnosis of histologic transformation of MALT lymphoma. Although transformation of t(11;18)-positive MALT lymphoma into aggressive lymphoma is extremely rare, it may occur, probably with additional genetic abnormalities such as cMYC rearrangement and/or the loss of TP53.

Lymphomas arising in immune-privileged sites: insights into biology, diagnosis, and pathogenesis

Session 2 of the 2018 European Association of Hematopathology/Society for Hematopathology Workshop focused on lymphomas arising in immune-privileged sites: both lymphomas arising in the traditionally described "immune sanctuary" sites of the central nervous system (CNS) and testes, as well as those arising at sites of local immune privilege. Primary CNS large B cell lymphoma and primary testicular large B cell lymphoma were discussed, and the biology of these unique tumors was highlighted by several cases showing the classic mutation profile including MYD88 L265P and CD79B. The tendency of these tumors to involve both the CNS and testis was also reinforced by several cases. Four cases of low-grade B cell lymphomas (LGBCL) of the CNS were discussed. Two were classic Bing-Neel syndrome associated with LPL, and two were LGBCL with plasmacytic differentiation and amyloid deposition without systemic disease. Rare examples of systemic T and NK cell lymphomas involving the CNS were also discussed. Several cases of breast implant-associated anaplastic large cell lymphoma (BI-ALCL) were submitted showing the typical clinicopathologic features. These cases were discussed along with a case with analogous features arising in a patient with a gastric band implant, as well as large B cell lymphomas arising alongside foreign materials. Finally, large B cell lymphomas arising in effusions or localized sites of chronic inflammation (fibrin-associated diffuse large B cell lymphoma [DLBCL] and DLBCL associated with chronic inflammation) were described. The pathogenesis of all of these lymphomas is believed to be related to decreased immune surveillance, either innate to the physiology of the organ or acquired at a local site.

Diffuse large B-cell lymphoma variants: an update

Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma, representing approximately one-third of all cases worldwide. In the World Health Organization (WHO) classification of lymphomas, most cases of DLBCL are designated as not otherwise specified (NOS). About 20% of cases, however, are designated as specific variants of DLBCL. These variants, 13 in total, are specified on the basis of distinctive morphological or immunophenotypic findings or distinctive biological or clinical issues associated with their diagnoses. In this review we discuss the following variants: T-cell/histiocyte-rich large B-cell lymphoma; ALK-positive large B-cell lymphoma; plasmablastic lymphoma; intravascular large B-cell lymphoma; large B-cell lymphoma with IRF4 rearrangement; primary mediastinal large B-cell lymphoma; primary cutaneous diffuse large B-cell lymphoma, leg type; primary diffuse large B-cell lymphoma of the central nervous system; diffuse large B-cell lymphoma associated with chronic inflammation; lymphomatoid granulomatosis; primary effusion lymphoma; and HHV8-positive diffuse large B-cell lymphoma, NOS. Two additional variants recognised in the WHO classification, EBV-positive diffuse large B-cell lymphoma and EBV-positive mucocutaneous ulcer are discussed elsewhere in another review within this issue of Pathology. Although not recognised as a specific variant in the current WHO classification, primary testicular diffuse large B-cell lymphoma also has unique biological features and requires some modification of the standard treatment approach for patients with DLBCL. Therefore, we suggest that primary testicular diffuse large B-cell lymphoma also should be recognised as a specific variant of DLBCL in a future version of the WHO classification.

Extraoral plasmablastic lymphomas in a high human immunodeficiency virus endemic area

AIMS

Plasmablastic lymphoma (PBL) occurs mainly in immunocompromised individuals, usually secondary to human immunodeficiency virus (HIV) infection. It classically occurs intraorally, but has been described in extraoral locations. The aim of this study was to define the immunophenotype and Epstein-Barr virus (EBV) status in a large single-centre cohort of extraoral PBL (EPBL) in South Africa, a high-prevalence HIV setting.

METHODS AND RESULTS

This retrospective study of 45 EPBLs included patients' age, gender, race, HIV status, and site. Cases were reviewed histologically, and classified morphologically as pure plasmablastic or plasmablastic with plasmacytic differentiation, and assessed immunohistochemically with antibodies against CD45, CD20, CD79a, PAX5, CD138, MUM1/IRF4, BLIMP1, VS38c, Ki67, bcl-6, CD10, cyclin D1, and human herpesvirus-8, by the use of standard automated procedures. EBV was assessed by the use of chromogenic in-situ hybridisation. Tumours were assessed with a fluorescence in-situ hybridisation (FISH) MYC break-apart probe. Twenty-seven PBLs showed pure plasmablastic morphology, and 18 showed plasmacytic differentiation. The male/female ratio was 1.5:1. The anus was the favoured extraoral site (31.1%), followed by lymph nodes (15.6%). All 29 patients with known HIV status were HIV-positive. The immunohistochemical profile recapitulated that reported for oral PBLs and EPBLs in HIV-positive and HIV-negative patients. EBV was positive in 92.5% of PBLs. FISH analysis showed MYC rearrangement in 48% of cases.

CONCLUSION

This study showed a strong association of EPBLs with HIV and EBV infection, similarly to the previously described oral PBL. The strong EBV association together with other clinicopathological parameters and an immunohistochemical profile that includes CD45, CD20, MUM1/IRF4, CD138 and Ki67 may be used in distinguishing PBL from diffuse large B-cell lymphoma and plasma cell myeloma.

CD3-positive diffuse large B-cell lymphoma relapses as CD3-negative large B-cell lymphoma: Loss of aberrant antigen expression in B-cell lymphoma after chemotherapy

Aberrant expression of CD3 on diffuse large B-cell lymphoma (DLBCL) is rare, and its mechanism and biological significance are currently unclear. Herein we report a case of Epstein-Barr virus-negative, CD3-positive DLBCL in a 53 year-old male, who had a remote history of renal transplantation. After standard chemotherapy, the patient was in clinical remission. He relapsed three years later, but at this time with apparent loss of CD3 expression. PCR-based IGK gene rearrangement studies demonstrated clonal amplicons with an identical nucleotide size between the primary and secondary DLBCL, confirming the clonal relationship despite their phenotypic differences. To our knowledge, this is the first case of CD3-positive DLBCL that demonstrated a loss of aberrant CD3 on relapse. The chronologic change in phenotype seen in this case suggests that the source of the patient's lymphoma relapse may arise from either a quiescent subclone without CD3 expression, or from an upstream neoplastic precursor cell.